Heat Sink Assembly

ABSTRACT

A heat sink assembly includes plural thermally conductive hair fins configured to be thermally coupled with a component to be cooled. The hair fins are elongated along a first direction and separated from each other by gaps along different second and third directions. The hair fins are configured to receive heat from the component to be cooled and to transfer the heat to cooling air disposed between the hair fins in order to cool the component.

FIELD

Embodiments of the subject matter disclosed herein relate to heat sinks,or components that assist in cooling other components.

BACKGROUND

Powered systems include components that generate heat. For example, somevehicles include electrical devices that generate heat during operationof the vehicles. These devices can include insulated gate bipolartransistors (IGBTs), rectifiers, or other solid state devices that cangenerate a significant amount of heat. Other heat-generating components,such as dynamic brakes or the like, also can generate significantamounts of heat.

In order to cool these components and allow the continued safe operationof the powered systems, heat sinks may be used to draw the heat awayfrom the components and thereby cool the components. Some heat sinksinclude elongated planar fins oriented in parallel with each other.These fins draw the heat from another component and dissipate the heatinto the surrounding atmosphere through the external surface areas ofthe fins.

One significant problem with some known heat sinks is the weight of theheat sinks. The heat sink weight can be a significant portion of thetotal weight of some powered systems. As one example, the cooling systemin a vehicle, such as a locomotive or other type of vehicle, of whichthe heat sinks are a large part, can constitute a significant portion ofthe weight of the locomotive, such as half of the total weight of thelocomotive. The large amount of heat sink weight can significantlyreduce the efficiency of operation of the powered systems.

BRIEF DESCRIPTION

In one embodiment, a heat sink assembly includes plural thermallyconductive hair fins configured to be thermally coupled with a componentto be cooled. The hair fins are elongated along a first directionextending away from the component and separated from each other by gapsalong different second and third directions that are orthogonal to thefirst direction. The hair fins have external dimensions that are longeralong the first direction than each of the second and third directions.The hair fins are arranged in an array that includes plural rows of thehair fins, with each row having a respective plurality of the hair finsthat are spaced apart from one another in the second direction, and therows being spaced apart from one another in the third direction. Thehair fins are configured to receive heat from the component to be cooledand to transfer the heat to cooling air disposed between the hair finsand flowing between the hair fins in the second and third directions, inorder to cool the component. Each of the hair fins has a length alongthe first direction of at least fifty-five millimeters and across-sectional area, defined by a plane of the second and thirddirections, of no more than 0.0009 square millimeters, and the heat sinkassembly has a fin density of the hair fins of at least seventy-seven ofthe hair fins per square centimeter within an area of the heat sinkassembly that includes the hair fins. Optionally, the length may be atleast two millimeters and no more than fifty-five millimeters.

In one embodiment, a heat sink assembly includes a housing havingopposing side walls and plural thermally conductive hair fins disposedin a grid between the side walls of the housing. The hair fins areconfigured to be thermally coupled with a component to be cooled. Thehair fins are elongated along a first direction and separated from eachother by gaps along different second and third directions. The hair finsare configured to receive heat from the component to be cooled and totransfer the heat to cooling air disposed between the hair fins in orderto cool the component.

In one example, the first direction extends away from the component, andthe second and third directions are orthogonal to one another and to thefirst direction. The hair fins can have external dimensions that arelonger along the first direction than each of the second and thirddirections. The hair fins can be arranged in the grid as an array thatincludes plural rows of the hair fins, with each row having a respectiveplurality of the hair fins that are spaced apart from one another in thesecond direction. The rows can be spaced apart from one another in thethird direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter described herein will be better understood fromreading the following description of non-limiting embodiments, withreference to the attached drawings, wherein below:

FIG. 1 illustrates one example of a plate type heat sink assembly;

FIG. 2 illustrates a hair fin type heat sink assembly according to oneembodiment of the inventive subject matter;

FIG. 3 illustrates another view of the hair fin type heat sink assemblyshown in FIG. 2;

FIG. 4 also illustrates the hair fin type heat sink assembly shown inFIG. 2;

FIG. 5 illustrates a hair fin shown in FIGS. 3 and 4 according to oneembodiment;

FIG. 6 illustrates the hair fins shown in FIGS. 3 and 4 with no air flowdirected between or across the hair fins;

FIG. 7 illustrates the hair fins shown in FIG. 6 with air flowing in afirst direction; and

FIG. 8 illustrates the hair fins shown in FIG. 6 with air flowing in anopposite second direction.

DETAILED DESCRIPTION

One or more embodiments of the inventive subject matter described hereinprovide heat sink assemblies having lightweight hairs to replace currentplate type heat sinks. This hair fin type heat sink assembly haspotential to significantly reduce or eliminate cooling air flowrequirements, as well as significantly reduce the weight and spaceneeded for the heat sink assemblies of powered systems. The hair fintype heat sink assemblies have higher surface-to-volume ratios whencompared to the plate type heat sinks, which can increase the heattransfer coefficient of the hair fin type heat sink assemblies by two ormore orders of magnitude over the plate type heat sink assemblies.Moreover, the hair fin type heat sink assemblies can reduce the weightof the heat sink assemblies (e.g., by 50% or more) and/or cooling airflow requirements significantly (e.g., 70% to 100% less air flow throughthe hair fins) when compared to plate type heat sink assemblies.

FIG. 1 illustrates one example of a plate type heat sink assembly 100.The plate type heat sink assembly 100 includes an outer housing 102 inwhich several elongated and planar plate type fins 104 are oriented inparallel with each other. The housing 102 is coupled with a component106 to be cooled by the heat sink assembly 100. The component 106 canrepresent an electrical device such as an IGBT, a rectifier, a dynamicbrake system, or the like, that generates heat. The plate type fins 104are planar bodies in that each of the fins 104 has much a much largerexternal dimension in each of two orthogonal directions 108, 110 than ina third orthogonal direction 112. For example, each of the plate typefins 104 shown in FIG. 1 can have an external dimension along thedirection 108 (e.g., between opposite front and back ends of the fin104) that is 215 millimeters, an external direction along the direction110 (e.g., between opposite top and bottom edges of the fin 104) that isfifty-five millimeters, and an external direction along the direction112 (e.g., between the opposite planar sides of the fin 104) that isonly two millimeters.

Heat generated in or by the component 106 is transferred to the platetype fins 104. Cooling air flows into the housing 102 through inlets 114of the housing 102. This air may be supplied from a fan, blower, etc.The cooling air flows within the gaps between the plate type fins 104and exits the housing 102 through an outlet 116 of the housing 102. Thecooling air draws heat in the plate type fins 104 from the component 106and carries at least some of this heat out of the heat sink assembly 100through the outlet 116.

A powered system, such as a vehicle (e.g., a locomotive, automobile,mining vehicle, etc.), may include several heat sinks. The plate typefin heat sink assemblies 100 can be significant contributors to theoverall weight of the powered system, and can require a significant flowof cooling air into the housing 102 in order to draw the heat off of theplate type fins 104.

FIGS. 2 through 4 illustrate a hair fin type heat sink assembly 200according to one embodiment of the inventive subject matter. The heatsink assembly 200 includes a housing 202 formed from parallel side walls204, 206 disposed on opposite sides of an array or field 208 of hairfins 300 (shown in FIGS. 3 and 4). The hair fins 300 are arranged in agrid or regular array in the field 208. For example, the hair fins 300that neighbor or are next to each other may be equidistantly spaced andseparated from each other by gaps along the direction 108 and along thedirection 112. Alternatively, the distance between neighboring hair fins300 may be larger in one direction 108 or 112 than the distance betweenneighboring hair fins 300 in the other direction 112 or 108.

FIG. 5 illustrates one of the hair fins 300 shown in FIGS. 3 and 4according to one embodiment. The hair fins 300 are elongated along onedirection by a much greater distance than the dimensions of the hairfins 300 along other orthogonal directions. For example, the hair fins300 may have an outer dimension 500 that is longer along the direction110 than outer dimensions 502, 504 of the hair fins 300 along either ofthe directions 108, 112. In one embodiment, the hair fins 300 may have asmall aspect ratio indicative of this elongation, such as a ratio of thewidth to the height of the hair fin 300 of less than 0.001, less than0.0008, less than 0.0006, or another value. One example of the hair fins300 has an outer dimension along the direction 110 of at leastfifty-five millimeters and an outer dimension along each of thedirections 108, 112 of no greater than 0.03 millimeters to provide anaspect ratio of 0.000545 and a cross-sectional area of 0.0009 mm².Alternatively, the hair fins 300 may have other dimensions. For example,the outer dimension along each of the directions 108, 112 may be nogreater than 0.1 micron or no greater than one micron.

The small cross-sectional area of the hair fins 300 in a plane definedby the directions 108, 112 allows for the hair fins 300 to be fairlyclose together in a dense arrangement. The density of the fins 300 inthe plane defined by the directions 108, 112 may be significantly large,such as at least 500 to no more than 2,000 fins 300 per square inch (orat least 77 fins 300 per square centimeter to no more than 310 fins 300per square centimeter). This large density of hair fins 300 allows thehair fin type heat sink assembly 200 to have a large heat flux density(e.g., the amount of heat that is drawn out of the air flowing betweenthe fins 300), such as a heat flux density of at least 500 watts persquare inch (or at least 77.5 watts per square centimeter), at least 700watts per square inch (or at least 108 watts per square centimeter), orup to 1,000 watts per square inch (or up to 155 watts per squarecentimeter).

The hair fins 300 may be formed from one or more thermally conductivematerials, such as aluminum or another metal or metal alloy. In oneembodiment, the hair fins 300 are formed from a flexible material thatallows the hair fins 300 to individually flex or bend with the flow ofair across the field of hair fins 300. The flexibility of the hair fins300 is shown in FIGS. 6 through 8. In FIG. 6, no air flow is directedbetween the hair fins 300. As a result, the hair fins 300 aresubstantially or completely vertically oriented. In FIG. 7, air flowsbetween the hair fins 300 from a left-to-right direction in theperspective of FIG. 7. In FIG. 8, air flows between the hair fins 300from a right-to-left direction in the perspective of FIG. 8. As shown inFIGS. 7 and 8, the hair fins 300 slightly change shape from a straightor linear shape to a bent shape. The flow of air against the hair fins300 changes the shape of the hair fins 300 due to the flexible nature ofthe hair fins 300.

As shown in FIG. 5, the hair fins 300 may have a square cross-sectionalshape in a plane that is parallel or defined by the directions 108, 112.Alternatively, the hair fins 300 may have a circular or othercross-sectional shape. The different cross-sectional shapes may dependon the pressure and/or rate of cooling air flowing through the field 208of hair fins 300.

In operation, the heat sink assembly 200 is coupled with the component106 to be cooled. The hair fins 300 are thermally coupled with thecomponent 106, such as by directly coupling the hair fins 300 with thecomponent 106 or by coupling the hair fins 300 with a thermallyconductive plate 302 that is coupled to the component 106. Cooling airis directed along a direction oriented between or parallel to theopposing side walls 204, 206 of the housing 202. This cooling air passesthrough and between the hair fins 300 along an inlet direction shown inFIG. 2. Due to the gaps between the hair fins 300 along multipledifferent directions, the cooling air is able to flow between the hairfins 300 in a direction that is opposite of the direction 112, in thedirection 108, and in the direction that is opposite of the direction108. This can allow for increased or more rapid cooling of the heattransferred from the component 106 to the hair fins 300 (relative to theplate type fins). The air may exit out of the heat sink assembly 200along a side of the field 208 that is opposite of the inlet. The sidewalls 204, 206 can constrain flow of the cooling air through the field208 to remain between the hair fins 300 from one end 210 of the field208 to the opposite end 212 of the field 208.

The hair fins 300 have been found to significantly increase heattransfer from the component 106 to the cooling air relative to platetype fins. The hair fins 300 provide considerably more surface areathrough which heat is transferred to the cooling air when compared tothe plate type fins. For example, the hair fins 300 may provide upwardof fifty or more times surface area than the plate type fins.

In one example, the component 106 generated heat in the amount of twowatts, and the hair fins 300 were found to cool a plate disposed betweenthe hair fins 300 and the component 106 to an average temperature ofninety-nine degrees Celsius, while the heat sink assembly 100 having theplate type fins only cooled the plate to an average temperature of 140degrees Celsius.

The hair fins 300 also can provide significantly higher heat transfercoefficients than the plate type fins. For example, the hair fins 300may provide a heat transfer coefficient of 11,000 or more.

Additionally, because of the many different paths that the cooling airmay take through the field 208 of hair fins 300, the amount, flow rate,or mass flow rate of the cooling air passing through the field 208 maybe less than that for the plate style fins, while still cooling thecomponent 106 as much or more than the plate style fins extending overthe same distance along the direction 112. For example, 70% or less ofthe air flow used to cool the component 106 using the plate style finsmay be used to cool the same component 106 by the same amount or morewhen using the hair fins 300.

A method for providing the heat sink assembly 200 may include obtainingseveral of the hair fins 300 and coupling the hair fins 300 to thecomponent 106 to be cooled. The hair fins 300 may be coupled with aplate that is then coupled with the component 106, or may be directlycoupled with the component 106. The hair fins 300 are separated fromeach other to allow cooling air to flow between the hair fins 300 alongplural different directions.

In one embodiment, a heat sink assembly includes plural thermallyconductive hair fins configured to be thermally coupled with a componentto be cooled. The hair fins are elongated along a first directionextending away from the component and separated from each other by gapsalong different second and third directions that are orthogonal to thefirst direction. The hair fins have external dimensions that are longeralong the first direction than each of the second and third directions.The hair fins are arranged in an array that includes plural rows of thehair fins, with each row having a respective plurality of the hair finsthat are spaced apart from one another in the second direction, and therows being spaced apart from one another in the third direction. Thehair fins are configured to receive heat from the component to be cooledand to transfer the heat to cooling air disposed between the hair finsand flowing between the hair fins in the second and third directions, inorder to cool the component. Each of the hair fins has a length alongthe first direction of at least fifty-five millimeters and across-sectional area, defined by a plane of the second and thirddirections, of no more than 0.0009 square millimeters, and the heat sinkassembly has a fin density of the hair fins of at least seventy-seven ofthe hair fins per square centimeter within an area of the heat sinkassembly that includes the hair fins.

In one example, the hair fins have square cross-sectional shapes in aplane defined by the second and third directions.

In one example, the assembly also includes a housing having opposingside walls on opposite sides of the hair fins.

In one example, the hair fins are arranged in a grid with the hair finsbeing equidistant from each other in the grid along the second and thirddirections.

In one example, the hair fins are separated from each other by firstdistances along the second direction and different, second distancesalong the third direction.

In one example, each of the hair fins has an aspect ratio of less than0.001.

In one example, the first direction is oriented perpendicularly to atleast one of the component or to a thermally conductive plate to whichthe hair fins are attached, the plate being configured for attachment tothe component.

In one embodiment, a heat sink assembly includes plural thermallyconductive hair fins configured to be thermally coupled with a componentto be cooled. The hair fins are separated from each other by gaps alongdifferent directions. The hair fins are configured to receive heat fromthe component to be cooled and to transfer the heat to cooling airdisposed between the hair fins in order to cool the component.

In one example, the different directions of the gaps, by which the hairfins are separated from each other, are orthogonal, and the hair finsare configured to receive the heat from the component to be cooled andto transfer the heat to the cooling air that flows along the differentorthogonal directions between the hair fins.

In one example, the hair fins are elongated along a direction that isorthogonal to the different orthogonal directions in which the coolingair flows.

In one example, the hair fins have square cross-sectional shapes in aplane defined by the different orthogonal directions.

In one example, the assembly also includes a housing having opposingside walls on opposite sides of the hair fins.

In one example, the hair fins are arranged in a grid with the hair finsbeing equidistant from each other in the grid along the differentorthogonal directions.

In one example, each of the hair fins has an aspect ratio of less than0.001.

In one embodiment, a heat sink assembly includes a housing havingopposing side walls and plural thermally conductive hair fins disposedin a grid between the side walls of the housing. The hair fins areconfigured to be thermally coupled with a component to be cooled. Thehair fins are elongated along a first direction and separated from eachother by gaps along different second and third directions. The hair finsare configured to receive heat from the component to be cooled and totransfer the heat to cooling air disposed between the hair fins in orderto cool the component.

In one example, hair fins are separated from each other by the gaps suchthat the cooling air flows between the hair fins in both the second andthird directions.

In one example, the hair fins have external dimensions that are longeralong the first direction than each of the second and third directions.

In one example, the hair fins are arranged in the grid with the hairfins being equidistant from each other in the grid along the second andthird directions.

In one example, each of the hair fins has an aspect ratio of less than0.001.

In one example, the first direction extends away from the component, andthe second and third directions are orthogonal to one another and to thefirst direction. The hair fins can have external dimensions that arelonger along the first direction than each of the second and thirddirections. The hair fins can be arranged in the grid as an array thatincludes plural rows of the hair fins, with each row having a respectiveplurality of the hair fins that are spaced apart from one another in thesecond direction. The rows can be spaced apart from one another in thethird direction.

The foregoing description of certain embodiments of the inventivesubject matter will be better understood when read in conjunction withthe appended drawings. The above description is illustrative and notrestrictive. For example, the above-described embodiments (and/oraspects thereof) may be used in combination with each other. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the inventive subject matter withoutdeparting from its scope. While the dimensions and types of materialsdescribed herein are intended to define the parameters of the inventivesubject matter, they are by no means limiting and are exampleembodiments. Other embodiments may be apparent to one of ordinary skillin the art upon reviewing the above description. The scope of theinventive subject matter should, therefore, be determined with referenceto the appended claims, along with the full scope of equivalents towhich such claims are entitled.

In the appended claims, the terms “including” and “in which” are used asthe plain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects. Further, thelimitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. § 112(f), unless and until such claim limitations expresslyuse the phrase “means for” followed by a statement of function void offurther structure. And, as used herein, an element or step recited inthe singular and proceeded with the word “a” or “an” should beunderstood as not excluding plural of said elements or steps, unlesssuch exclusion is explicitly stated. Furthermore, references to “oneembodiment” of the inventive subject matter are not intended to beinterpreted as excluding the existence of additional embodiments thatalso incorporate the recited features. Moreover, unless explicitlystated to the contrary, embodiments “comprising,” “including,” or“having” an element or a plurality of elements having a particularproperty may include additional such elements not having that property.

This written description uses examples to disclose several embodimentsof the inventive subject matter and also to enable a person of ordinaryskill in the art to practice the embodiments of the inventive subjectmatter, including making and using any devices or systems and performingany incorporated methods. The patentable scope of the inventive subjectmatter is defined by the claims, and may include other examples thatoccur to those of ordinary skill in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal languages of the claims.

What is claimed is:
 1. A heat sink assembly comprising: plural thermallyconductive hair fins configured to be thermally coupled with a componentto be cooled, the hair fins being elongated along a first directionextending away from the component and separated from each other by gapsalong different second and third directions that are orthogonal to thefirst direction, wherein the hair fins have external dimensions that arelonger along the first direction than each of the second and thirddirections, wherein the hair fins are arranged in an array that includesplural rows of the hair fins, each row having a respective plurality ofthe hair fins that are spaced apart from one another in the seconddirection, and the rows being spaced apart from one another in the thirddirection, wherein the hair fins are configured to receive heat from thecomponent to be cooled and to transfer the heat to cooling air disposedbetween the hair fins and flowing between the hair fins in the secondand third directions, in order to cool the component, and wherein eachof the hair fins has a length along the first direction of at least twomillimeters and no more than fifty-five millimeters and across-sectional area, defined by a plane of the second and thirddirections, of no more than 0.0009 square millimeters, and the heat sinkassembly has a fin density of the hair fins of at least seventy-seven ofthe hair fins per square centimeter within an area of the heat sinkassembly that includes the hair fins.
 2. The heat sink assembly of claim1, wherein the hair fins have square cross-sectional shapes in a planedefined by the second and third directions.
 3. The heat sink assembly ofclaim 1, further comprising a housing having opposing side walls onopposite sides of the hair fins.
 4. The heat sink assembly of claim 1,wherein the hair fins are arranged in a grid with the hair fins beingequidistant from each other in the grid along the second and thirddirections.
 5. The heat sink assembly of claim 1, wherein the hair finsare separated from each other by first distances along the seconddirection and different, second distances along the third direction. 6.The heat sink assembly of claim 1, wherein each of the hair fins has anaspect ratio of less than 0.001.
 7. The heat sink assembly of claim 1,wherein the first direction is oriented perpendicularly to at least oneof the component or to a thermally conductive plate to which the hairfins are attached, the plate being configured for attachment to thecomponent.
 8. A heat sink assembly comprising: plural thermallyconductive hair fins configured to be thermally coupled with a componentto be cooled, the hair fins separated from each other by gaps alongdifferent directions, wherein the hair fins are configured to receiveheat from the component to be cooled and to transfer the heat to coolingair disposed between the hair fins in order to cool the component. 9.The heat sink assembly of claim 8, wherein the different directions ofthe gaps, by which the hair fins are separated from each other, areorthogonal, and wherein the hair fins are configured to receive the heatfrom the component to be cooled and to transfer the heat to the coolingair that flows along the different orthogonal directions between thehair fins.
 10. The heat sink assembly of claim 9, wherein the hair finsare elongated along a direction that is orthogonal to the differentorthogonal directions in which the cooling air flows.
 11. The heat sinkassembly of claim 9, wherein the hair fins have square cross-sectionalshapes in a plane defined by the different orthogonal directions. 12.The heat sink assembly of claim 9, further comprising a housing havingopposing side walls on opposite sides of the hair fins.
 13. The heatsink assembly of claim 9, wherein the hair fins are arranged in a gridwith the hair fins being equidistant from each other in the grid alongthe different orthogonal directions.
 14. The heat sink assembly of claim9, wherein each of the hair fins has an aspect ratio of less than 0.001.15. A heat sink assembly comprising: a housing having opposing sidewalls; and plural thermally conductive hair fins disposed in a gridbetween the side walls of the housing, the hair fins configured to bethermally coupled with a component to be cooled, the hair fins beingelongated along a first direction and separated from each other by gapsalong different second and third directions, wherein the hair fins areconfigured to receive heat from the component to be cooled and totransfer the heat to cooling air disposed between the hair fins in orderto cool the component.
 16. The heat sink assembly of claim 15, whereinthe hair fins are separated from each other by the gaps such that thecooling air flows between the hair fins in both the second and thirddirections.
 17. The heat sink assembly of claim 15, wherein the hairfins have external dimensions that are longer along the first directionthan each of the second and third directions.
 18. The heat sink assemblyof claim 15, wherein the hair fins are arranged in the grid with thehair fins being equidistant from each other in the grid along the secondand third directions.
 19. The heat sink assembly of claim 15, whereineach of the hair fins has an aspect ratio of less than 0.001.
 20. Theheat sink assembly of claim 15, wherein: the first direction extendsaway from the component, and the second and third directions areorthogonal to one another and to the first direction; the hair fins haveexternal dimensions that are longer along the first direction than eachof the second and third directions; and the hair fins are arranged inthe grid as an array that includes plural rows of the hair fins, eachrow having a respective plurality of the hair fins that are spaced apartfrom one another in the second direction, and the rows being spacedapart from one another in the third direction.